Apart from interest in the basic biology of the process, understanding the mechanism and regulation of DNA replication is important for medicine. We know that cancer is primarily a genetic disease caused by mutations and one source of these mutations is defects in DNA replication and repair. Genetic instability may also be a factor in some neurodegenerative diseases and in ageing. Proteins involved in DNA replication may be at high levels in cells that are dividing rapidly, and detecting such proteins can be useful in screening for some diseases such as cancer. Drugs that inhibit DNA replication and thus slow cell division are useful for treating some types of cancer. Also, since viruses may use different enzymes to replicate their genomes, anti-viral drugs can also exploit differences between human and virus replication proteins.

In eukaryotes (cells with nuclei), chromosomes are replicated in a specific phase of the cell cycle (S- for synthesis - phase). Replication starts from a large number of replication origins, from which replication proceeds in both bidirectionally until the region between the origins is completely replicated.  Replication is carried out by enzymes which unwind the DNA (helicase) and do the copying (polymerases). A large number of other proteins are involved to ensure that this process is regulated correctly and occurs with high fidelity so that very few mistakes are made in the copying process. DNA replications is also involved in other chromosomal processes such as recombination, which is necessary for gamete (sperm and egg) production, and DNA repair.